Hitherto, in electronic apparatuses, for example, IC driving voltages have decreased and circuit currents have increased, and chopper (switching) DC-DC converters having excellent conversion efficiency have been widely used. A chopper DC-DC converter, which is formed mainly of a combination of a switching device, a power inductor, a capacitor, a diode, and the like, steps down or steps up (converts) a given DC voltage to a desired DC voltage.
In designing a DC-DC converter, a circuit simulator has been utilized to verify design requirements such as ripple voltage and over-current limit. Various simulation methods for a DC-DC converter which uses a power inductor have been proposed. For example, refer to the following non-patent documents:    (1) B. M Hasaneen and Adel A. Elbaset Mohammed, “DESIGN OF SIMULATION OF DC/DC BOOST CONVERTER”, Power System Conference, 2008, MEPCON 2008, 12th International Middle-East, IEEE, Mar. 12, 2008, pp. 334-340.    (2) Christophe Batard, Frederic Politiers, Christophe Millet, and Nicolas Ginot, “MATLAB-A Fundamental Tool for Scientific Computing and Engineering Applications-Volume 1 (Chapter 3) Simulation of Power Converters Using Matlab-Simulimk”, INTECH, Sep. 26, 2012, PP. 43-68.